A main objective of the present proposal is the elucidation and chemical analysis of maturation changes in the sperm plasma membrane in the epididymis and uterus. Similar studies will be carried out on the egg plasma membrane and zona pellucida in the hours before ovulation, following establishment of the "zona reaction" at fertilization, and during post-ovulatory ageing of the unfertilized egg. These observations will be extended to include the blastomere surface and ultimately trophoblastic and endometrial surfaces to determine the possible biophysical correlates and evidence for increasing adhesiveness of these surfaces as the time of implantation approaches. Secondly, we will investigate the specificity and nature of the factors influencing fusion of the sperm membranes during the acrosome reaction, fusion of the sperm with the plasma membrane of the vitellus as well as the development of the male pronucleus in the egg. Investigation of the mechanisms responsible for sperm transport from the vagina to cervix will be undertaken in addition to studies of the particular importance of the character and species specificity of the sperm surface for efficient passage through cervical mucus.